Possessive

English

There are two ways to form a possesive in English.
A) Add an apostrophe + s after a single noun.
     Mary's dress.
     a tree's branches

B) Add an apostrophe + s after a plural noun that does not already end in s.
    the children's playground
    the men's department.

C) Add an apostrophe after the s in a plural noun if it ends in s.
    the students' teacher
    the girls' club

Use the words of the or of a   before the word that is the possessor.  It does not matter if the word is singular or plural.
     the book of the professor
     the branches of a tree
     the teacher of the students

Spanish


In Spanish there is no apostrophe.  You can only from a possessive using the second example above.

In order to construct the possessive you structure is:
the noun possessed + de ("of") + article + the noun possessor.

Mary's dress = el vestido de María.
(the dress of Mary)
the professor's book = el libro del profesor  (del = de + el)
(the book of the professor)
the lady's purse = la bolsa de la señora
(the purse of the lady)
a tree's branches = las ramas de un árbol
(the branches of the tree)
the girl's father = el padre de las muchachas
(the father of the girls)